The invention relates to a rotary transformer, comprising an inner core portion which is enclosed by an outer core portion, which core portions are formed as hollow bodies of revolution of a ferro-magnetic material which are rotatable with respect to one another about a common axis, their facing surfaces being constructed as conical surfaces provided with first recesses which are shaped as a staircase with substantially flat steps on which transformer windings are provided, the windings on the inner core portion and the outer core portion being situated opposite one another and cooperating in a two-by-two fashion, the windings on at least the outer core portion being constructed as self-supporting coils.
A transformer of this kind is known from the abstract in English of JP-A 59-151,408. The new types of scanners used in a video recorder require a rotary signal transfer device (RSO) comprising a large number of channels. If the known transformer were to be used for this purpose, the dimensions thereof would become rather large whereas the space available to the rotary signal transfer device is limited.